title: Working length changes in curved canals after coronal flaring by using rotary files and hand file: An in vitro study.
abstract: OBJECTIVE
  This in vitro investigation examined the effect of early coronal flaring (CF) and late CF on the working length (WL) in curved root canals.
  
  
  BACKGROUND
  The objective of this study was to determine if canal length is altered as a result of CF in curved canals of molar roots.
  
  
  METHODS
  The conditions compared were combinations of (a) stainless steel hand files using Gates Glidden (G. G.) drills (SS) versus nickel-titanium rotary files (Ni-Ti); and (b) early CF (flaring completed before WL determination) versus late CF (flaring completed after WL determination). Selected were 90 canals of extracted maxillary or mandibular first molars (mesial root of mandibular molars and the mesiobuccal root of the maxillary molars) from three groups. CF was accomplished for the SS group using G. G. drills and for the Ni-Ti group using rotary ProTaper and Hero Shaper files. WL was determined by a digital vernier caliper before CF, immediately after CF, and again after canal preparation.
  
  
  METHODS
  A repeated measures analysis of variance (ANOVA) test and a Tukey's multiple prosthoc test were used for this study.
  
  
  RESULTS
  Results indicated that WL decreased for all canals as a result of canal preparation. The mean decrease in WL was significantly greater for the SS group (-0.77 ± 0.42 mm) than for the Ni-Ti groups (-0.33 mm ± 0.44). Less change in WL occurred in all groups when initial WL was determined after CF.
  
  
  CONCLUSIONS
  WL in curved canals consistently decreases during the course of instrumentation. Clinician should keep this in mind for better treatment outcome.
authors.affiliation: Department of Conservative Dentistry and Endodontics, Mahatma Gandhi Mission's Dental College and Hospital, Navi Mumbai, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Kumar
authors.forename: Neha
authors.initials: N
authors.lastname: Khambete
authors.forename: Suvarna
authors.initials: S
authors.lastname: Patil
authors.forename: Upendra
authors.initials: U
authors.lastname: Hoshing
authors.forename: Ashish
authors.initials: A
authors.lastname: Medha
authors.forename: Roshan
authors.initials: R
authors.lastname: Shetty
keywords: Hero shaper; ProTaper; precoronal flaring; root canal preparation; rotary files; working length